Early versus late diagnosis in infectious encephalitis: A population-based cohort study

AbstractObjectives To investigate the clinical characteristics and outcomes of patients with early versus late diagnosis of infectious encephalitis in Denmark. Methods Nationwide, prospective, population-based cohort study using the Danish Study Group for Infections of the Brain database to identify all adults hospitalized with infectious encephalitis from 2015-2023. Late diagnosis was defined as lumbar puncture or initiation of acyclovir treatment >6 hours after admission, and very late diagnosis >24 hours after admission. Unfavourable outcome was defined as Glasgow Outcome ScaleResults Infectious encephalitis was identified in 495 patients of whom 183/495 (37%) were categorized as early diagnosis and 312/495 (63%) as late diagnosis. Median time to diagnosis was 12 hours (interquartile range IQR 4-43). Patients with late diagnosis were older compared to those with early diagnosis (72 years, IQR 61-79 vs 65 years, IQR 43-75). A late diagnosis was less likely in patients presenting with GCS 24 hours after admission was associated with increased mortality at 30 days (Adj. RR 2.20; 95% CI 1.16-4.19) and six months (Adj. RR 1.59 95%CI 1.06-2.39). Conclusion Late diagnosis of infectious encephalitis remains common and is associated with older age and absence of altered mental status at admission. Receiving a diagnosis >24 hours after admission is associated with increased risk of 30-day and 6-month mortality.